.game {
    position: relative;
    width: 800px;
    height: 600px;
    border: 1px #333 solid;
    margin: 10px auto;
    overflow: hidden;
}

.sky {
    position: absolute;
    top: 0;
    left: 0;
    width: 200%;
    height: 100%;
    background: url("./img/sky.png");
}

.land {
    position: absolute;
    width: 200%;
    height: 112px;
    left: 0;
    bottom: 0;
    background: url("./img/land.png");
    z-index: 2;
}

.pipe {
    position: absolute;
    width: 52px;
    height: 200px;
}

.pipe.up {
    left: 650px;
    top: 0;
    background:url("./img/pipeDown.png");
    background-position: bottom;
}

.pipe.down {
    left: 650px;
    bottom: 0;
    background: url("./img/pipeUp.png");
}

.bird {
    position: absolute;
    top: 250px;
    left: 300px;
    width: 36px;
    height: 26px;
    background: url("./img/bird.png");
}

.bird.swing1 {
    background-position: -7px -10px;
}

.bird.swing2 {
    background-position: -59px -10px;
}

.bird.swing3 {
    background-position: -112px -10px;
}

.info {
    text-align: center;
}

.mask {
    position: absolute;
    width: 800px;
    height: 600px;
    z-index: 999;
    left: 0;
    top: 0;
    background: rgba(0, 0, 0, .5);
    color: #fff;
    font-size: 40px;
    text-align: center;
    line-height: 600px;
    display: none;
}

.counter {
    position: absolute;
    right: 0;
    top: 0;
    width: 120px;
    height: 40px;
    text-align: center;
    line-height: 40px;
    z-index: 998;
}